Quenching oils



ice

3,027,315 Patented Mar. 27, 1902 3,027,315 QUENCHING OILS Hugh Rodman, Oakmont, Pa,, and Hugh Rodman, Jan, Plainfield, NJ. Filed Nov. 3, 1953, Ser. No. 390,016 5 Claims. (Cl. 20814) This application is a continuation-in-part of our copending application Serial No. 91,466 filed May 5, 1949, now abandoned, and sets forth an invention which relates to oils used for quenching and hardening steel, and has for an object the production of new. and improvedv quenching oils which have hardening abilities far greater than those of any oils known today.

Great hardness is necessary in many steel parts which must withstand wear and abrasion. Such parts as bearings, axles, wearing strips, gears, guides, etc., usually must be machined to form them, and this operation is impossible or prohibitively expensive if the metal is hard. Therefore these parts are formed or Shaped while the metal is soft and then heat treated to develop the maximum hardness consistent with the desired toughness.

Some steels, particularly those having high alloy content and consequently high cost, do not require rapid cooling or quenching in their heat treatment to develop hardiness. To harden the cheaper and more commonly used steels, however, it is usually necessary that they be heated above their critical temperatures and then quenched rapidly. The quenching operation may be conveniently described as consisting of three steps, each removing about one third of the heat. The first step sets the hardness as the steel cools rapidly through its critical temperatures. The second step draws or reduces the hardness, and the degree of softening depends upon the rate of cooling. The third step, if slow enough, tempers the hard steel and minimizes distortion in this temperature range where volume changes occur. The first step is short, the second longer, and the third much longer.

Water is the oldest quenching medium and is very much faster than any oil, but it has the disadvantage that it usually warps steel parts and. frequently cracks them. Such spoilage is common and costly. As the design of the steel part becomes more intricate, particularly where there is much contrast between thick and thin sections and also where there are sharp corners, this warping and cracking eiiect becomes so pronounced as to make water quenching impractical.

In the search for a suitable medium for hardening steel effectively without undue distortion or cracking, many offorts have been made to increase the initial quenching speed of oils or oil blends.

Oil as a quenching medium has the valuable characteristic of cooling steel exceedingly slowly, compared to water, after the temperature ofthe steel has been reduced to about 600 to 700 F. This quality in oil, this cushioning of the cooling rate in the lower temperature range where distortion and cracking occur if the rate is, rapid, appears to be the reason why oil-quenched steel, compared to water-quenched steel, is relatively free from warping and cracking.

A slight advance in the search for a hardening medium was made by blending small amounts of lard oil,

wool grease, etc., with non-viscous petroleum fractions. A considerable advance was made by Rodman and Boren (US. Patent 1,535,379) in 1925 by blending about 10% of heavy petroleum bottom stock with the same base oils. There the advance apparently ended, and the commercial blends made in accordance with this 1925 disclosure have since remained among the fastest and most eifective of available quenching oils.

Great as this advance was, however, it left much to be desired. These modern oils can harden the plain carbon steels, from low carbon content through tool steel, only about 30% as effectively as water.

There is a strong need in the heat treating art for a quenching medium having a much greater hardening ability than the best of the presently known quenching oils but which will have a cooling rate in the lower temperature ranges as low or lower than these oils so as to avoid Warping or cracking steel parts.

A specific object of our invention is a. quenching oil which produces great hardness in many types of steel which respond poorly to treatment with the best of present-day and previously-known oils.

Another object is a quenching oil which can increase the hardness in many types of steel far beyond that ohtainable with the best of present-day and previouslyknown oils, even through the hardness presently attainable with these oils may have been regarded as satisfactory, until now, because nothing better was known.

A further object is the production of new and improved quenching oils which are not only highly eifective inhardening. steel parts of various types, sizes and shapes, but which accomplish such hardening Without sacrificing the freedom from warping and cracking which distinguishes oil from water as quenching media.

A still further objective of our invention is the production of a quenching oil having unusually great hardening ability, lacking in tendency to produce warping or cracking of metal parts quenched in it, and possessing so much more fluidity than the usual quenching oils that the loss of oil adhering to quenched metal parts withdrawn from the bath (usually called carry-out oil) is greatly reduced.

These and other objects, made apparent. by the further description of our invention, are attained by the new oil blends herein defined. As evidence of the attainment of these objects, We here tabulate the viscosity, in Saybolt Universal seconds at F., of several oils and and the hardness produced by them in quenching 1.25" sections of two common steels, viz., SAE 1035 and 1% carbon tool steel.

Our invention consists in the production of a quenching and hardening oil having a much lower viscosity than any of the modern fast quenching oils and which hardens many types and sizes of steel about twice as efiectively as any oil now known without sacrificing the advantage oils have over water as a quenching and hardening medium in the avoidance of cracking and warping the quenched part. The new oil includes one or more petroleum fractions or other oils having a lower viscosity than any base oil heretofore employed and is blended with 'small amounts of additives such as are ordinarly employed in quenching oil to increase the initial quenching speed thereof.

To make the invention clear it is necessary to describe the methods now used to estimate the hardening ability of quenching oils.

One method commonly used is the five second quenching test. It consists of a calorimetric determination of the percentage of total heat removed from inch-diameter metal at 1500 F. when it is immersed for five seconds in oil or other coolants. This percentage of heat removal, probably covering the hardening portion of the quench, was considered to be indicative of the hardening ability of the coolant tested. See US. Patent 2,327,383 issued to zur Horst et al. in 1943 for a description of this test. A variation of this test has been incorporated in the specifications describing the US. Army Ordnance Departments requirements for quenching oil. The percentage determination will hereinafter be referred to as IQS (initial quenching speed). Oils having IQS above 36 have been usually called fast oils. Our investigations indicate that this test is to some extent useful up to an IQS of 30, for oils of the usual viscosity range, i.e., 90 to 200 SUS at 100 F., but is of little significance above that and is of no significance in connection with our new oils. We have used it for indications only, relying upon hardness determinations for direct evidence of hardening ability.

Although our new quenching oil blends have been employed in hardening many types and sizes of steel, most of our investigations as to the handening ability of such oils and of known commercial quenching oils have been conducted by employing a standardized hardening procedure. This procedure involves employing a solid cylinder of hot-rolled SAE 1035 steel 1.25" diameter and 1" long, with both ends faced off and polished. It is heated for 75 minutes at 1525 F. in a carefully controlled atmosphere of carbon monoxide and carbon dioxide adjusted to minimize both carburization and decarburization of the metal. Then it is immersed in 600 grams of still oil at about 100 F. and allowed to cool while so immersed. After lightly polishing the ends of the piece, at least four Brinell hardness tests are made on these polished surfaces,

and averaged. Alternatively, six hardness determinations are made with a Rockwell tester, using the C scale, and averaged. Although it is common practice to convert one kind of hardness measurement to another by using charts which make approximate comparisons, this practice can be highly misleading because, if the hardness varies with depth (and this is usual) or is shallow, a tester such as the Scleroscope, which does not penetrate the steel to any appreciable extent, will indicate a much greater hardness than a Brinell tester which penetrates much deeper. All hardness tests reported herein were made with the kind of tester stated and none of the results has been converted.

'SAE 1035 steel was selected because no commercial quenching oil known to us can harden it by the test described above to more than 260 Brinell or 32 Rockwell C, whereas water can harden it to 512 Brinell or 52 Rockwell C; In its dead soft condition this metal is 160 Brinell. This wide range in hardness provides a convenient measure by which the relative hardening abilities of quenching oils may be compared. However, the use of other metals such as SAE 1042 or Water-hardening tool-steel give comparable results.

If the test is performed with some metal other than SAE 1035 and quenched from a temperature suitable for hardening that metal, but otherwise performed the same as in the standardized test, then these results will be reported so as to show what metal and what quenching temperature was used, for example, SAE 1045 Brinellhardness 1520 F.

Following is a table showing comparative results when three different metals, originally in dead soft condition, were hardened in various quenching media by the procedure described in the standardized hardening test.

By comparing the hardness produced by the various hardening agents, as measured in the lines designated Points above soft, it can be seen that the new oil blend has at least twice the hardening ability of the modern fast oil.

We refer here to the following United States patents:

Rodman et al., No. 1,535,379, April 28, 1925 Rodman, No. 1,818,431, Aug. 11, 1931 zur Horst et al., No. 2,327,383, Aug. 24, 1943 zur Horst et al., No. 2,327,977, Aug. 24, 1943 zur Horst et al., No. 2,340,726, Feb. 1, 1944 These patents disclose quenching oils made by blending small amounts of heavy petroleum products or other additives with mineral base oils having viscosities as low but no lower than 70 Saybolt Universal seconds at F. We note that these and other patents relating to quenching oils speak of consistency measurements in terms of Saybolt Universal seconds at 100 F. Hereafter in this application, the term viscosity will refer to consistencies determined by this test at this temperature, in seconds.

The emphasis in all these patents is upon the additives which are blended with base oils and also upon the effect these additives have on the five second initial quenching speed test. Other patents dealing with quenching oils speak only vaguely, if at all, about evidence of the worth of the oils as quenching media. They do, however, speak of suitable viscosities within the range of 100 to 200. There is no evidence in the claims or specifications of these or any other patents of which we are aware that the viscosity of the base oils was considered to be of any importance except as it was related to such secondary characteristics as flash point and carry-out loss. All these base oils fall within a class of petroleum distillates generally known as non-viscous neutrals, which are relatively cheap and have flash-points well above the usual working temperatures of quenching oil baths. To the best of our knowledge 70 is the lowest viscosity ever used or considered practicable for quenching oil bases, although more viscous oils were frequently used. Most commercial quenching oils made and used when the above mentioned patents issued, as well as those made and used now, have viscosities varying between 85 and 120, and some are considerably more viscous.

There are many additives now in general use which are compatible with the low viscosity base oils employed by us and which may be utilized in producing new oil blends which constitute embodiments of our invention. These additives may be employed alone or in combination. In general, an effective additive is a high molecular weight substance such as residues from the refining of petroleum, heat treated vegetable oils, some resins and similar substances which, when added in small proportions to base oils such as the petroleum non-viscous neutral fractions, materially increases their IQS, presumably by suppressing the formation of gases at the surfaces of the red-hot metals introduced into the blends.

The preferred embodiment of our invention consists of a mineral base oil having a viscosity much lower than that of .any base oil heretofore used, preferably about 38. to 45, blended with a small amount, preferably about 5%, of an additive capable of increasing the IQS of the blend, preferably to 30 to 35, the final blend having a viscosity between about 40 and 50 seconds.

In proving our invention, a number of mineral oils were employed each having a viscosity substantially lower than that of oils ordinarily. employed as quenching oil bases. To 100 parts of each such base oil was added 5 parts of an additive which was known to be effective. Identical pieces of SAE 1035 steel were heated to 1525 F. and were quenched in equal quantities of each of these blends at 100 F. They were examined for hardness and a graph was drawn plotting the hardness against the viscosity of the respective base oils employed in the blend.

The drawing accompanying and forming a part hereof is a graph such as is above referred to in which the Brinell-hardness developed by the various blends are plotted as ordinates and the viscosities of the difierent base oils, as designated by Saybolt Universal seconds at 100 F., are plotted as abscissas.

The curve indicated by these points peaks sharply when the base oil viscosity is about 39 to 42. Below this maximum the curve drops off rapidly. This drop-off is probably due to the lower boiling range which ischaracteristic of lower viscosity. oils. If the oil is very low-boiling and is.used anywhere near its boiling temperature, it vaporizes adjacent to the hot steel so rapidly that the steel is insulated from the oil.by a vapor blanket. Hot water alsoacts this way. Similarly, kerosene having a viscosity less than 32 andused at 100 F. gives very poor hardening results alone or when blended with a normally effective additive.

The following table presents the results of the tests described above; these results were used for plotting the. curve in the drawing.

Although the foregoing table shows that optimum hardening elfect is reached 'with blends made from base oils having viscosities from'about 39 to 42, we have discovered that, in a group of base oils within this viscosity range, some prove to be more satisfactory than others in hardening effect when blended with suitable additives Attention is called to the third column in the above,

table which shows centistokes, or absolute viscosities, rather than the arbitrary though usual Saybolt seconds. Using this scale, our new quenching oil at its best performance is about four times more fluid than the usual fast quenching oils.

It is not known with certainty what characteristics.

maintained at 210 F., however, showed no increase whatever in hardness over that produced by the same oil when used at its normal working temperature of F. Thus it appears that (within reasonable limits) the bardening effect of an oil is not dependent upon the viscosity of the oil in the quenching bath, as determined by its working temperature, but is probably due to or strongly influenced by its viscosity at some much higher temperature reached when it touches the red-hot or nearly red-hot steel.

The following table compares two modern commercial fast quenching oils with various blends of a lowviscosity base oil mixed with different amounts of an effective additive. The two modern oils were chosen from those having the fastest known IQS and are favorably known commercial products. The heat removal tests were conducted in the same manner as the standrd QS est e cept hat the l ch w e. r

periods of 5, 10 and 20 seconds. The Brinell-hardness numbers shown are for the standard 1.25" diameter cylinders 1" long of SAE 1035 steel quenched from 1525 F. and a well known brand of water-hardening tool steel (1.00% carbon) quenched from 1450 F. From the table it will be plain that there is no clear relationship. between IQS and the hardness which develops in the.

steels quenched in our new blends. For instance, one

of the two modernoils has an IQS of 38.5 and toolsteel quenched in it is only 400 hard, whereas the new lowviscosity base oil blended with 3% of the additive has only 31 IQS but makes the same steel 600 hard.

There appears to be a relationship between the hard ness developed and the amount of heat removed during the second five-second-periodof the quench. With the exception of our new blends, none of the many quenching oils examined by us has a percentage-of-heat-reinoval during the 5 to 10 second interval of the quench greater than 13%. The more effective blends of our new lowviscosity mixtures, however, remove about 19 to 23% of the heat during this same interval. After the first five seconds of the quench in any reasonably effective quenching medium, the temperature of the steel is probably below the critical range where the hardness is set. During the second five-second-period the steel passes through an intermediate temperature range which may be described as a high temperature drawing (softening) range. Faster passage through this elevated drawing heat may allow a greater preservation of the hardness (or conditions making for hardness) induced during the first five seconds.

V Percentage Heat Removal Time Intervals Brinell-Hardness 1s., SUS, 100 F. -5 0-10 0-20 -10 -20 SAE Tool Secs. Secs. Secs. Secs. Secs. 1035 Steel Dead Soft 160 200 Oil N0. 1 106 37. 5 50. 3 63 12. 8 12. 7 256 405 Oil N0. 2 90 38. 5 50. 6 64 12.1 13. 4 260 400 Thin Base-Oil Only- 41. 5 10. 5 20. 2 51 9 7 30. 8 200 TBO and 1% A".-- 42. O 14 40 64 26 24 210 TBO and 2% A. 42. 5 21 50. 5 68. 3 29. 5 17. 8 299 375 TBO and 3% A 43.2 31 54 68 23 14 360 600 TBO and 5% A. 44. 2 36. 5 56 67. 5 19. 5 11. 5 360 600 T130 and 7.5% A 45. 5 39 57. 5 67. 5 18. 5 10 356 580 TBO and 10% A. 47. 2 39 56 67.5 17 11. 5 348 510 TBO and 12.5% A." 49 36. 5 55 5 67 19 11. 5 327 500 TBO and A 52 85 55 66. 5 20 ll. 5 322 490 Norse:

TBO is thin base oil. A is the additive. All bath temperatures were initially 100 F.

As an example of this invention, one blend we have found effective is made as follows: Blend 3 to 5 parts of steam-refined cylinder stock (a residiuum from the refining of Pennsylvania petroleum, having a flash point of 650 F., a Saybolt Universal viscosity of 440 seconds at 210 F., and a dark green color), with 100 parts of a low viscosity base oil such as is used in coke-oven gas stripping operations as an absorbent oil (having a flash point of 265 F., a viscosity of 41.5, and an almost waterwhite color). This produces a blend having a flash point of 270 F. and a viscosity about 44. This blend hardens steel much more successfully than the fastest previously known quenching oils. Steel test pieces 1.25" in diameter and 1" long were prepared of SAE 1035 steel and also of water-hardening tool steel having about 1.00% carbon. These were heated to correct temperatures in a furnace with a controlled atmosphere and quenched in the new blend and in several fast modern oils at 100 F. The results of the hardness tests are tabulated below.

Similar tests upon other sizes and other steels and other blends and at other oil temperatures gave comparable results.

' A blend similar to the one referred to in the above table as improved blend has been used by a large commercial heat treating company for a great variety of quenching jobs on steel articles of varying complexity ranging in weight from a few ounces to eighty pounds each. Many of these jobs were the so-called heat treaters nightmare. This term is usually applied to parts having sharp corners, thick and thin sections, and made of water-hardening steel. On such jobs it is almost impossible to get the desired hardness with any presently known oil, yet if water is employed as the quenching medium, the risk of cracking and the near certainty of warping are great. With such parts or articles it is often necessary to make a very short quench in water followed by a finishing quench in oil. Such treatment is difficult to plan properly, difficult to duplicate, usually results in considerable warping, and is unsatisfactory in other ways. Our new oil blend produces in most water-hardening steels hardness as high as it is practical to have without danger of excessive brittleness. These hardnesses far exceed the greatest which can be produced with the usual fast oils. Following is a brief description of some of the jobs done commercially.

(1) Contour rolls about 3%" diameter by 5 /2" long weighing about 11 pounds each, made of .90 carbon tool steel, quenched in the new oil from 1520 F. were 61/62 Rockwell C.

(2) Large screws, each having a flat head about 1%" thick and about 10" in diameter, a threaded section about 4 /2" in diameter and about 6 long with a square thread cut about /2 deep, and several smaller diameter sections with sharp shoulders, each weighing about eighty pounds. These were SAE 4615 steel, carburized to a depth of A Quenched from 1450 F. in the new oil the Scleroscope showed 82/84. Note: This result would normally require a brine quench.

' (3) Gripper plates about /8" x 1%" x 3", each'weighing about /2 pound, made of .75 carbon steel, were quenched in the new oil from 1440 F. to get 61/63 Rockwell C.

(4) Bevel gears, about 10 pounds each, made of SAE 1045 steel, were quenched in the new oil from 1520 to get a Brinell hardness of 500. Normally the best prior oils could produce only about 330-350.

(5) Rolls, 5" in diameter, 2" thick, 1%" hole in center, two flanges square machined into the cylindrical surface with sharp corners, made of .90 carbon steel, were quenched from 1450 in the new oil. The hardness developed was 61/ 63 Rockwell C, whereas the best old-style oil could not produce more than 45.

Following is a description of a test which indicates that our improved oil blend allows a great increase in hardness without appreciable loss of strength in quenched stee Five 5" long pieces of cold rolled SAE 1042 steel square, each cut from the same bar, were quenched from 1520 F. One was quenched in cold water, another in the new oil, the third in a fast modern oil, the fourth in a slow oil, and the fifth was annealed dead soft. Each was then supported in a horizontal position between two blocks 3 /2" apart, and then broken or bent by'pushing down on the middle of the unsupported section with a.

. steadily descending hydraulic ram. The pieces were examined at the breaks or cut in the middle if bent but not broken; the water-quenched piece showed uniform structure over the entire'area of the break, the piece quenched in the modern so-called fast oil showed a uniform but difierent structure over its entire crosssection, but the piece quenched in the improved oil'blend showed a definite case about /s" deep resembling the water-quenched break, while the core resembled the break of the piece quenched in modern oil. Each break or cut was then carefully ground smooth and examined with a Rockwell tester. Then each piece was examined on its 9 outside surface by the Rockwell and Brinell methods. Following is a tabulation of the results:

coolants. The procedure for these tests was that of the Five Second Test. The tabulated results follow.

Water is tap water at 80 F.

New Blend is the blend described in the example and called Improved Blend.

Usual Oil is a fast modern commercial quenching oil.

Poor Oil is a 70 viscosity non-viscous neutral with no additive.

The temperature of these oil baths was 100 F.

Annealed is dead soft condition.

One disadvantage inherent in the use of quenching oils having viscosities of 90 or over is that their quenching speeds lessen as their temperatures drop much below 100 F., possibly because of an increase in voscosity. Therefore, quenching tanks left idle overnight and therebycooled, say to 70 F., must be heated if irregular and incomplete hardening is to be avoided. It is not usual practice to provide quenching tanks with means for heat ing the quenching medium. Our improved low-viscosity blends function successfully down to 40 F. or even lower.

Loss of quenching oil in service is due to cracking of the oil, with consequent production of sludge, and to carry-out, i.e., oil adhering to the quenched steel. The latter is much the more important, especially when the parts are small or thin.

We have encountered no cracking of the oil or sludge formation.

The absolute viscosity of the usual modern quenching oils at 100 F., is about centistokes, whereas the preferred absolute viscosity of our new blend is only about 5 centistokes at the same temperature. The carry-out is related to viscosity.

In laboratory tests and in commercial use the loss of the new low-viscosity blends from quenching operations is less than half that suifered with other commercial oils. Therefore it lasts more than twice as long and for this reason alone it is Worth more than twice as much.

Low viscosity oils ordinarily have low flash points and boiling ranges, and it was at first feared that our improved quenching oil with about 45 viscosity and 270 flash-point would be a fire hazard. However, the use of this oil in an important heat-treating establishment has dispelled this fear. The improved quenching oil was first used in a nearly filled open-top drum with no means for cooling. Large and small steel sections were quenched under such conditions and at times the temperature of the oil in the drum rose above 200 F- The same rise in temperature has since occurred in much larger tanks when a number of eighty-pound articels were quenched in rapid succession. No fire or flashing or other trouble has occurred. Since most quenching oil tanks are agitated to prevent accumulation of hot oil at the surface and are maintained at about 120 F. by well-known and effective cooling apparatus, it is certain that our improved quenching oil can be used safely.

Extensive commercial use has demonstrated that our improved quenching oil blend is as free, if not freer, of distortion-producing qualities as fast modern quenching oils. In order to compare its quenching rate with those of a commercial fast oil and Water, heat-removal tests were made for many time intervals on these three Percent Heat Removed, 18-8 Test Pieces Quenching Time, Seconds New Oil Best Tap Water, I

If these heat removal test results are plotted against time, it can be seen that, compared with the two oil curves, the cooling curve of Water drops like a plummet. Closer examination reveals that after 10 seconds the cooling curve of the new oil blend is slightly slower than that of the fast commercial oil.

Moredirect evidence was gained by quenching special test pieces designed to exaggerate the distortion efiect of ditferent quenching-media. Such test pieces distorted about 10% less in our new improved blend than in the usual modern quenching oils when they were quenched under normal working conditions.

All this evidence agrees with behavior in commercial use.

It is evident-that certain quenching operations require oils producing hardness between the highest (except for water) described in this application and that obtainable with the best of previously known oils. A variety of new oil blends capable of producing Brinel -hardness from 260 up to 365 or more may be prepared by blending different quantities of various effective additives with a preferred low-viscosity base oil, or else by using low-viscosity base oils of different viscosities to each of which is added a quantity of addititive chosen to produce the best hardening efiect for that particular oil. Each of these new blends surpasses in hardening ability any commercially available quenching oils heretofore known. We, therefore, propose to manufacture oil blends having viscosi ties anywhere below 65 down to but not including the very thin oils such as kerosene, the flash-point and boiling range of which are so low as to interfere with its quenching action.

For the purpose of simplifying the wording of the claims, we recapitulate and define in the following glossary the meaning of terms used in this specification and in the appended claims.

Glossary Quenching oil.An oil or oil blend used as a coolant in a bath where red-hot steel, above its critical temperatures, is immersed to cool it rapidly and thereby harden it.

IQS.-The initial quenching speed of a coolant as determincd by the standard five second quenching test. This test is a calorimetric detennination of the percentage of aavilable heat removed from a certain 1500' F. test piece when it is quenched or immersed for 5 seconds in the coolant initially at F.

10 second speezL-A test identical to the standard five second quenching test (IQS) except that the quench ing time interval is ten seconds instead of five.

Terminal portion of the quench.ln heat removal tests identical to the standard five second quenching test except that the quenching time intervals are different, that portion of the quenching occurring between about 20 and seconds after the start of the quench.

Base oil.The principal constituent of a quenching oil.

Additive.--Any substance or mixture of substances which can be blended in minor proportions with a base oil to increase its IQS and hardening ability.

Mineral oil.Oil of mineral origin as opposed to oil of animal or vegetable origin. Mineral oil ordinarily means petroleum oil or certain fractions thereof separated'by the customary fractionation methods such as distillation, solvent extraction, crystallization, and the like, but we mean the term mineral oil to include also petroleum-like oils or fractions thereof which are derived from other mineral sources such as coal or shale or natural gas, as well as petroleum-like oils or fractions thereof which are synthetic in origin.

Viscsity.Consistency at 100 M. measured in seconds by the Saybolt Universal viscosimeter.

. COC.The Cleveland open cup method for determining flash-point.

Brinell-hardness.'l'he hardness at each end of a 1%" diameter solid cylinder of SAE 1035 steel 1" long which has been heated in a protective atmosphere for 75 minutes at 1525 F., completely quenched without agitation in 600 grams of the coolant, initially at 100 F. then lightly polished and measured with a Brinell hardness tester, using a millimeter diameter ball and a load of 30 kilograms.

' Carry-OuL-A normal loss suffered because of oil adhering to quenched metal articles withdrawn from a quenching oil bath.

What we claim is:

i 1. A quenching oil blend for use in the hardening of steel having an IQS ranging from about 30 to about 40, a 10 second speed in excess of 52 and consisting of a mineral base oil having a viscosity within the range of from about 38 to about 45 SUS at 100 F. and from about 2% to about 10% of an IQS-increasing additive.

' 2. A quenching oil blend for use in the hardening of steel having an IQS within the range of from about 30 to about 40, a 10 second speed of at least 52, a viscosity within the range of from about 40 to about 50 SUS at 100 F. and consisting of a mineral base oil having a viscosity of from about 38 to SUS at 100 F. blended with from about 2% to about 10% of an IQS-increasing additive.

3. A quenching oil blend for use in the hardening of steel having a viscosity within the range of from about 40 to about SUS at F. and an IQS from about 30 to about 35 and consisting of about 5% of an IQS- increasing additive and a mineral base oil having a viscosity of from about 38 to about 45 SUS at 100 F.

4. A new and improved quenching oil having a viscosity of about 42 SUS at 100 F., a COC flash point of about 265 F. and which consists of about 100 parts of a petroleum base oil having a viscosity of about 40 SUS at 100 F. and a COC flash point of about 260 F.; and about 5 parts of a heavy petroleum bottom stock having a viscosity of about 440 seconds at 210 F. and a COC flash point of about 650 F.

5. A quenching oil blend for use in the hardening of steel and having an IQS within the range of from about 31 to about 39; a 10 second speed within the range of from about 54 to about 57.5; a viscosity ranging from about 43.2 SUS at 100 F. to about 45.5 SUS at 100 F; and consisting of 100 parts of a mineral base oil having a viscosity of 45.5 SUS at 100 F., blended with from 3 to 7.5% of an IQS-increasing additive.

References Cited in the file of this patent UNITED STATES PATENTS Mar-ms...

UNITED STATES PATENT OFFICE CERTIFICATE, OF CORRECTION Patent No. 3,027,315 March 27, 1962 Hugh Rodman et a1.

It is hereby certified that error appears in the above numbered pctent requiring correction and that the said Letters Patent should read as corrected belcw.

Column 3, line 11, for "ordinarly" read ordinarily column 9, line 27, for "voscosity" read viscosity column 10, line 63, for "aavilable" read available column 11, line 14, for "100 M. read 100 F.

Signed and sealed this 14th day of August 1962.,

(SEAL) Attcet:

ERNEST W. SWIDER DAVID L. LADD Attesting Officer Commissioner of Patents 

1. A QUENCHING OIL BLEND FOR USE IN THE HARDENING OF STEEL HAVING AN IQS RANGING FROM ABOUT 30 TO ABOUT 40, A 10 SECOND SPEED IN EXCESS OF 52 AND CONSISTING OF A MINERAL BASE OIL HAVING A VISCOSITY WITHIN THE RANGE OF FROM ABOUT 38 TO ABOUT 45 SUS AT 100*F. AND FROM ABOUT 2% TO ABOUT 10% OF AN IQS-INCREASING ADDITIVE. 